The communications arrangements and methods of the related applications provide a network access arrangement in which access to a CSMA/CD (Carrier Sense Multiple Access with Collision Detection) network, such as the Network using Ethernet frames, is provided via a telephone line by providing a master modem at the head end and a slave modem at the subscriber end of the line, and in which crosstalk with communications on other telephone lines can be reduced. The master modem provides a CSMA/CD interface to the Network and controls half duplex, or burst mode, communications with the slave modem via the line to avoid collisions of Ethernet frames on the line. The Ethernet frames are enveloped in frames on the line with error checking information; control information between the modems is contained in the same and/or in separate frames. Multiple Ethernet frames can be concatenated in a single frame on the line. The modulation method and signal bandwidth can be varied depending on errors to provide optimum conmmunications capacity via any particular line, and a ratio of upstream to downstream frames can be varied depending on buffer fills at the modems. The modulated signal frequencies are above telephone signal frequencies so that each telephone line can be frequency diplexed for simultaneous telephone communications.
In such communications arrangements, as in any communications system, it is desirable to provide, for the two directions of communication, an optimum, e.g. the greatest possible, capacity consistent with avoiding errors both in this communications arrangement and in other communications arrangements with which there may be crosstalk.
Object of this invention are to provide improved methods of transmitting information and improved communications apparatus.